Studies of the measurement and partial characterization of steroid hormone binding to macromolecules in target tissues have provided the basis for this project, which is directed toward an investigation of specific steroid hormone binding in normal human uterine tissues as compared to endometrial or endometrioid cancer. It is known that some endometrial tumors regress following progestin treatment while others do not. We propose to measure the blood levels of estradiol and progesterone and the uterine binding proteins of these hormones in patients from whom uterine tissues are obtained. The various parameters of these two types of hormones binding proteins in uterine tissue will also be examined in patients with postmenopausal endometrial atrophy and with endometrial or endometrioid cancer after the administration of estrogens. These results will be correlated with histological changes in the endometrium and also with the response of these tumors to hormone therapy. It is our presumption that estrogens will increase the level of progesterone binding proteins in normal and neoplastic endometrial tissues, and provide a rational basis for altering the traditional clinical treatment of these forms of cancer.